Vocal learning is important for socialization in man and also in several bird species. Birds which display vocal learning depend on auditory input for the development and maintenance of adult song. The major auditory pathways in the bird brain have been described and we have recently characterized some brain regions involved in the motor control of song. We do not presently know at what points in the central nervous system auditory information acts to modify vocal output. These experiments will investigate the neural links between auditory and vocal brain regions using a wide variety of neuroanatomical techniques. Two such techniques, amino acid tracer autoradiography and horseradish peroxidase, have only recently been adopted for use in neuroanatomy but promise to greatly facilitate the tracing of CNS connections. Proposed neuroanatomical investigations include: 1) tracing the connections of telencephalic vocal control areas using amino acid transport, Golgi stains (to demonstrate short axons) and variants of the Fink-Heimer stain to demonstrate degenerating terminals: 2) tracing projections to vocal control areas using horseradish peroxidase injections: and 3) examining autoradiographic, horseradish peroxidase, Golgi and Fink-Heimer material for the commisural fibers that must exist to co-ordinate song production by the two hemispheres. The dependence of learned vocalizations on hearing in some birds has suggested that the development of neural connections between auditory vocal areas must underly the evolution of vocal learning. Results of these experiments may suggest neuroanatomical loci for these evolutionary changes. In addition, the learned nature of bird song and motor control by special telencephalic regions suggests analogies with human speech. These neuroanatomical studies will aid in evaluating the usefulness of such an avian model system.